Outboard motor control apparatus

ABSTRACT

In an apparatus for controlling operation of an outboard motor having an internal combustion engine and a transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, it is determined whether acceleration is instructed to the engine when the second speed is established and operation of the engine is controlled to increase a fuel amount to be supplied to the engine when detected engine speed is greater than a predetermined speed, thereby improving the performance immediately after acceleration is started.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an outboard motor control apparatus, particularly to an apparatus for controlling an outboard motor with a transmission.

2. Description of the Related Art

In recent years, there is proposed an outboard motor equipped with a transmission, which has the gear position to establish first speed and second speed, interposed at a location between an internal combustion engine and propeller shaft to change output of the engine in speed and then transmit it to the propeller shaft, as taught, for example, by Japanese Laid-Open Patent Application No. 2009-190671.

SUMMARY OF THE INVENTION

In the reference, when a throttle lever is manipulated by the operator to accelerate the boat, the gear position (gear ratio) of the transmission is changed from the second speed to the first speed to amplify torque to be transmitted to the propeller shaft, thereby improving the acceleration performance.

However, if the gear position is changed from the second speed to the first speed when the boat speed has already reached the medium level (intermediate speed) and the engine speed is relatively high, a propeller does not grip water so that the boat speed decreases without giving accelerating feel to the operator. This is disadvantageous and it still leaves room for improvement in terms of the acceleration performance.

An object of this invention is therefore to overcome the foregoing drawbacks by providing an apparatus for controlling an outboard motor having a transmission, which apparatus can appropriately control the operation of the transmission and an internal combustion engine during acceleration, thereby improving performance immediately after acceleration is started.

In order to achieve the object, this invention provides in its first aspect an apparatus for controlling operation of an outboard motor adapted to be mounted on a stern of a boat and having an internal combustion engine to power a propeller through a propeller shaft, and a transmission installed at a location between the engine and the propeller shaft, the transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, comprising: an engine speed detector that detects speed of the engine; an acceleration instruction determiner that determines whether acceleration is instructed to the engine when the second speed is established; and a controller that controls operation of the engine to increase a fuel amount to be supplied to the engine when the detected engine speed is greater than a predetermined speed.

In order to achieve the object, this invention provides in its second aspect a method for controlling operation of an outboard motor adapted to be mounted on a stern of a boat and having an internal combustion engine to power a propeller through a propeller shaft, and a transmission installed at a location between the engine and the propeller shaft, the transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, comprising the steps of: detecting speed of the engine; determining whether acceleration is instructed to the engine when the second speed is established; and controlling operation of the engine to increase a fuel amount to be supplied to the engine when the detected engine speed is greater than a predetermined speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the invention will be more apparent from the following description and drawings in which:

FIG. 1 is an overall schematic view of an outboard motor control apparatus including a boat according to an embodiment of the invention;

FIG. 2 is an enlarged sectional side view partially showing the outboard motor shown in FIG. 1;

FIG. 3 is an enlarged side view of the outboard motor shown in FIG. 1;

FIG. 4 is a hydraulic circuit diagram schematically showing a hydraulic circuit of a transmission mechanism shown in FIG. 2;

FIG. 5 is a flowchart showing transmission control operation and fuel increasing control operation by an electronic control unit shown in FIG. 1; and

FIG. 6 is a time chart for explaining the operation of the FIG. 5 flowchart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of an outboard motor control apparatus according to the invention will now be explained with reference to the attached drawings.

FIG. 1 is an overall schematic view of an outboard motor control apparatus including a boat according to a first embodiment of the invention. FIG. 2 is an enlarged sectional side view partially showing the outboard motor shown in FIG. 1 and FIG. 3 is an enlarged side view of the outboard motor.

In FIGS. 1 to 3, a symbol 1 indicates a boat or vessel whose hull 12 is mounted with an outboard motor 10. As clearly shown in FIG. 2, the outboard motor 10 is clamped (fastened) to the stern or transom of the hull 12 through a swivel case 14, tilting shaft 16 and stern brackets 18.

An electric steering motor (actuator) 22 for operating a shaft 20 which is housed in the swivel case 14 to be rotatable about the vertical axis is installed above the swivel case 14. A rotational output of the steering motor 22 is transmitted to the shaft 20 via a speed reduction gear mechanism 24 and a mount frame 26, whereby the outboard motor 10 is steered about the shaft 20 as a steering axis to the right and left directions (steered about the vertical axis).

An internal combustion engine (hereinafter referred to as the “engine”) 30 is disposed in the upper portion of the outboard motor 10. The engine 30 comprises a spark-ignition, water-cooling gasoline engine with a displacement of 2,200 cc. The engine 30 is located above the water surface and covered by an engine cover 32.

An air intake pipe 34 of the engine 30 is connected to a throttle body 36. The throttle body 36 has a throttle valve 38 installed therein and an electric throttle motor (actuator) 40 for opening and closing the throttle valve 38 is integrally disposed thereto.

The output shaft of the throttle motor 40 is connected to the throttle valve 38 via a speed reduction gear mechanism (not shown). The throttle motor 40 is operated to open and close the throttle valve 38, thereby regulating the flow rate of the air sucked in the engine 30 to control engine speed NE of the engine 30.

The outboard motor 10 further comprises a propeller shaft (power transmission shaft) 44 that is supported to be rotatable about the horizontal axis and attached with a propeller 42 at its one end to transmit power output of the engine 30 thereto, and a transmission (automatic transmission) 46 that is interposed at a location between the engine 30 and propeller shaft 44 and has the gear position to establish three speeds, i.e., first, second and third speeds.

The transmission 46 comprises a transmission mechanism 50 that can selectively change the gear position to establish the three speeds including the first to third speeds, and a shift mechanism 52 that can change a shift position among forward, reverse and neutral positions.

FIG. 4 is a hydraulic circuit diagram schematically showing a hydraulic circuit of the transmission mechanism 50.

As shown in FIGS. 2 and 4, the transmission mechanism 50 comprises a parallel-axis type transmission mechanism with distinct gear ratios, which includes an input shaft 54 connected to the crankshaft (not shown in the figures) of the engine 30, a countershaft 56 connected to the input shaft 54 through a gear, and an output shaft 58 connected to the countershaft 56 through several gears. Those shafts 54, 56, 58 are installed in parallel.

The countershaft 56 is connected with a hydraulic pump (gear pump; shown only in FIG. 2) 60 that pumps up the operating oil (lubricating oil) and forwards it to transmission clutches and lubricated portions of the transmission mechanism 50 (explained later). The foregoing shafts 54, 56, 58, hydraulic pump 60 and the like are housed in a case 62 (shown only in FIG. 2). An oil pan 62 a for receiving the operating oil is formed at the bottom of the case 62.

In the so-configured transmission mechanism 50, the gear installed on the shaft to be rotatable relative thereto is fixed on the shaft through the transmission clutch so that one of the gear positions (i.e., first to third speeds) is established (selected), and the output of the engine 30 is changed with the established (selected) gear position and transmitted to the propeller 42 through the shift mechanism 52 and propeller shaft 44. A gear ratio (speed reduction ratio) of the gear position is set to be the highest in the first speed and decreases as the gear position changes to second and then third speed. Specifically, for instance, the first speed gear ratio is 2.2, the second speed gear ratio 2.0, and the third speed gear ratio 1.7.

The further explanation on the transmission mechanism 50 will be made. As clearly shown in FIG. 4, the input shaft 54 is supported with an input primary gear 64. The countershaft 56 is supported with a counter primary gear 66 to be meshed with the input primary gear 64, and also with a counter first-speed gear 68, counter second-speed gear 70 and counter third-speed gear 72.

The output shaft 58 is supported with an output first-speed gear 74 to be meshed with the counter first-speed gear 68, an output second-speed gear 76 to be meshed with the counter second-speed gear 70, and an output third-speed gear 78 to be meshed with the counter third-speed gear 72.

In the above configuration, when the output first-speed gear 74 supported to be rotatable relative to the output shaft 58 is brought into a connection with the output shaft 58 through a first-speed clutch C1, the first speed (gear; gear position) is established. The first-speed clutch C1 comprises a one-way clutch (or sprag clutch). When a second-speed or third-speed hydraulic clutch C2 or C3 (explained later) is supplied with hydraulic pressure so that the second or third speed is established and the rotational speed of the output shaft 58 becomes greater than that of the output first-speed gear 74, the first-speed clutch C1 makes the output first-speed gear 74 rotate idly (i.e., rotate without being meshed).

When the counter second-speed gear 70 supported to be rotatable relative to the countershaft 56 is brought into a connection with the countershaft 56 through the second-speed hydraulic clutch C2, the second speed (gear; gear position) is established. Further, when the counter third-speed gear 72 supported to be rotatable relative to the countershaft 56 is brought into a connection with the countershaft 56 through the third-speed hydraulic clutch C3, the third speed (gear; gear position) is established. The hydraulic clutches C2, C3 connect the gears 70, 72 to the countershaft 56 upon supply of the operating oil, while making the gears 70, 72 rotate idly when the operating oil is not supplied.

The interconnections between the gears and shafts through the clutches C1, C2, C3 are performed by controlling hydraulic pressure supplied from the pump 60 to the hydraulic clutches C2, C3.

The further explanation will be made with reference to FIG. 4. An intake port 60 a of the pump 60 is connected to the oil pan 62 a through an oil passage 80 a. The oil passage 80 a is interposed with a strainer 82.

A discharge port 60 b of the pump 60 is connected to a first switching valve 84 a through an oil passage 80 b and the first switching valve 84 a is connected to a second switching valve 84 b through an oil passage 80 c. Each of the valves 84 a, 84 b has a movable spool installed therein. The spool is urged by a spring at its one end (left end in the drawing) toward the other end.

The first and second switching valves 84 a, 84 b are connected on the sides of the other ends of the spools with first and second electromagnetic solenoid valves (linear solenoid valves) 86 a, 86 b through oil passages 80 d, 80 e, respectively. The solenoid valves 86 a, 86 b are interposed at oil passages 80 f, 80 g which are branched from the oil passage 80 b.

The second switching valve 84 b is connected to the second-speed hydraulic clutch C2 through an oil passage 80 h, while being connected to the third-speed hydraulic clutch C3 through an oil passage 80 i.

The discharge port 60 b is also connected to the lubricated portions (e.g., the shafts 54, 56, 58, etc.) of the transmission 46 through the oil passage 80 b and an oil passage 80 j branched therefrom. The oil passage 80 j is interposed with a regulator valve 88 that regulates hydraulic pressure to be supplied to the lubricated portions, and a relief valve 90 that, when the hydraulic pressure of the operating oil regulated by the regulator valve 88 becomes equal to or greater than prescribed pressure, returns the operating oil to the oil pan 62 a.

The first and second switching valves 84 a, 84 b and the first and second solenoid valves 86 a, 86 b are connected with an oil passage 80 k adapted to relieve pressure and an end of the oil passage 80 k is open at the oil pan 62 a.

As configured above, the pump 60 driven by the engine 30 (more exactly, the countershaft 56 of the transmission 46 transmitted with the output of the engine 30) pumps up the operating oil in the oil pan 62 a through the oil passage 80 a and strainer 82 and forwards it from the discharge port 60 b to the first switching valve 84 a and the first and second solenoid valves 86 a, 86 b through the oil passage 80 b and the like. The pump 60 also supplies the operating oil (lubricating oil) to the lubricated portions of the transmission 46 through the oil passage 80 j, regulator valve 88 and relief vale 90.

Upon being supplied with current (i.e., made ON), a spool housed in the first solenoid valve 86 a is displaced to output the hydraulic pressure supplied from the pump 60 to the other end side of the spool of the first switching valve 84 a. The spool of the first switching valve 84 a is displaced in response to the hydraulic pressure outputted to its other end side, thereby forwarding the operating oil in the oil passage 80 b to the oil passage 80 c.

Similarly to the first solenoid valve 86 a, upon being supplied with current (i.e., made ON), a spool of the second solenoid valve 86 b is displaced to output the hydraulic pressure supplied from the pump 60 to the other end side of the spool of the second switching valve 84 b.

When the second solenoid valve 86 b is made ON and the hydraulic pressure is outputted to the other end side of the spool of the second switching valve 84 b so that the spool is displaced, the operating oil in the oil passage 80 c is forwarded to the second-speed hydraulic clutch C2 through the oil passage 80 h. In contrast, when the second solenoid valve 86 b is not supplied with current (made OFF) and the hydraulic pressure is not outputted to the other end side, the second switching valve 84 b forwards the operating oil in the oil passage 80 c to the third-speed hydraulic clutch C3 through the oil passage 80 i.

Consequently, when the first and second solenoid valves 86 a, 86 b are both made OFF, the hydraulic pressure is not supplied to the hydraulic clutches C2, C3 and hence, the output first-speed gear 74 and output shaft 58 are interconnected through the first-speed clutch C1 so that the first speed is established.

When the first and second solenoid valves 86 a, 86 b are both made ON, the hydraulic pressure is supplied to the second-speed hydraulic clutch C2 and accordingly, the counter second-speed gear 70 and countershaft 56 are interconnected so that the second speed is established. As mentioned in the foregoing, when the second speed is established and the rotational speed of the output shaft 58 exceeds that of the output first-speed gear 74, the gear 74 is disconnected from the shaft 58 by the first-speed clutch C1 and therefore rotated idly.

Further, when the first solenoid valve 86 a is made ON and the second solenoid valve 86 b is made OFF, the hydraulic pressure is supplied to the third-speed hydraulic clutch C3 and accordingly, the counter third-speed gear 72 and countershaft 56 are interconnected so that the third speed is established. As in the case of the second speed, the output first-speed gear 74 is rotated idly. Thus, one of the gear positions of the transmission 46 is selected (i.e., transmission control is conducted) by controlling ON/OFF of the first and second switching valves 84 a, 84 b.

The explanation on FIG. 2 is resumed. The shift mechanism 52 comprises a drive shaft (vertical shaft) 52 a that is connected to the output shaft 58 of the transmission mechanism 50 and installed parallel to the vertical axis to be rotatably supported, a forward bevel gear 52 b and reverse bevel gear 52 c that are connected to the drive shaft 52 a to be rotated, a clutch 52 d that can engage the propeller shaft 44 with either one of the forward bevel gear 52 b and reverse bevel gear 52 c, and other components.

The interior of the engine cover 32 is disposed with an electric shift motor (actuator) 92 that drives the shift mechanism 52. The output shaft of the shift motor 92 can be connected via a speed reduction gear mechanism 94 with the upper end of a shift rod 52 e of the shift mechanism 52. When the shift motor 92 is operated, its output appropriately displaces the shift rod 52 e and a shift slider 52 f to move the clutch 52 d to change the shift position among the forward, reverse and neutral positions.

When the shift position is forward or reverse, the rotational output of the output shaft 58 is transmitted via the shift mechanism 52 to the propeller shaft 44 to rotate the propeller 42 in one of the directions making the hull 12 move forward or rearward. The outboard motor 10 is equipped with a power source (not shown) such as a battery or the like attached to the engine 30 to supply operating power to the motors 22, 40, 92, etc.

As shown in FIG. 3, a throttle opening sensor (throttle opening change amount detector) 96 is installed near the throttle valve 38 and produces an output or signal indicative of opening of the throttle valve 38, i.e., throttle opening TH.

A neutral switch 100 is installed near the shift rod 52 e and produces an ON signal when the shift position of the transmission 46 is neutral and an OFF signal when it is forward or reverse. A crank angle sensor (engine speed detector) 102 is installed near the crankshaft of the engine 30 and produces a pulse signal at every predetermined crank angle.

The outputs of the foregoing sensors and switch are sent to an Electronic Control Unit (ECU) 110 disposed in the outboard motor 10. The ECU 110 which has a microcomputer comprising a CPU, ROM, RAM and other devices is installed in the engine cover 32 of the outboard motor 10.

As shown in FIG. 1, a steering wheel 114 is installed near a cockpit (the operator's seat) 112 of the hull 12 to be manipulated or rotated by the operator (not shown). A steering angle sensor 116 attached on a shaft (not shown) of the steering wheel 114 produces an output or signal corresponding to the steering angle applied or inputted by the operator through the steering wheel 114.

A remote control box 120 provided near the cockpit 112 is equipped with a shift/throttle lever (throttle lever) 122 installed to be manipulated by the operator. The lever 122 can be moved or swung in the front-back direction from the initial position and is used by the operator to input a forward/reverse change command and an engine speed regulation command including an acceleration/deceleration command (or instruction) for the engine 30. A lever position sensor 124 is installed in the remote control box 120 and produces an output or signal corresponding to a position of the lever 122.

A switch 126 is also provided near the cockpit 112 to be manually operated by the operator to input a fuel consumption decreasing command for decreasing fuel consumption of the engine 30. The switch 126 is manipulated or pressed when the operator desires to travel the boat 1 with high fuel efficiency, and upon the manipulation, it produces a signal (ON signal) indicative of the fuel consumption decreasing command.

A boat speed sensor (speedometer for water) 130 is installed at an appropriate position of the hull 12 and produces an output or signal corresponding to speed or velocity (boat speed; hereinafter sometimes called the “actual velocity”) V of the boat 1. The outputs of the sensors 116, 124, 130 and switch 126 are also sent to the ECU 110.

Based on the inputted outputs, the ECU 110 controls the operation of the motors 22, 40, 92 and performs the transmission control of the transmission 46. Further, based on the inputted outputs, the ECU 110 determines a fuel injection amount of the engine 30 to supply fuel by the determined injection amount from an injector 132 (shown in FIG. 3).

Thus, the outboard motor control apparatus according to the embodiments is a Drive-By-Wire type apparatus whose operation system (steering wheel 14, lever 122) has no mechanical connection with the outboard motor 10.

FIG. 5 is a flowchart showing the transmission control operation and fuel increasing control operation by the ECU 110. The illustrated program is executed by the ECU 110 at predetermined intervals, e.g., 100 milliseconds.

The program begins at S10, in which it is determined whether the shift position of the transmission 46 is neutral. This determination is made by checking as to whether the neutral switch 100 outputs the ON signal. When the result in S10 is negative, i.e., it is determined to be in gear, the program proceeds to S12, in which the throttle opening TH is detected or calculated from the output of the throttle opening sensor 96, and to S14, in which a change amount (variation) DTH of the detected throttle opening TH per a unit time (e.g., 500 milliseconds) is detected or calculated.

The program proceeds to S16, in which it is determined whether the deceleration is instructed to the engine 30 by the operator, i.e., whether the engine 30 is in the operating condition to decelerate the boat 1. This determination is made by checking as to whether the throttle valve 38 is operated in the closing direction, i.e., whether the change amount DTH is less than a first predetermined value DTHref1 (e.g., −0.5 degree).

Specifically, when the change amount DTH is less than the first predetermined value DTHref1 set to a negative value, the throttle valve 38 is determined to be operated in the closing direction (i.e., the deceleration is instructed to the engine 30) and when the change amount DTH is equal to or greater than the first predetermined value DTHref1, the throttle valve 38 is determined to be substantially stopped or operated in the opening direction (i.e., the deceleration is not instructed).

When the result in S16 is negative, the program proceeds to S18, in which it is determined whether the bit of an after-acceleration third-speed changed flag (explained later; hereinafter called the “third speed flag”) which indicates that the gear position has been changed to the third speed after the acceleration was completed, is 0. Since the initial value of this flag is 0, the result in S18 in the first program loop is generally affirmative and the program proceeds to S20.

In S20, the output pulses inputted from the crank angle sensor 102 are counted to detect or calculate the engine speed NE and in S22, a change amount (variation) DNE of the engine speed NE is calculated. The change amount DNE is obtained by subtracting the engine speed NE detected in the present program loop from that detected in the previous program loop.

Next, the program proceeds to S24, in which it is determined whether the bit of an after-acceleration second-speed changed flag (hereinafter called the “second speed flag”) is 0. The bit of this flag is set to 1 when the gear position is changed to the second speed after the acceleration is completed (explained later), and otherwise, reset to 0.

Since the initial value of the second speed flag is also 0, the result in S24 in the first program loop is generally affirmative and the program proceeds to S26, in which it is determined whether the engine speed NE is equal to or greater than a first gear change predetermined speed (hereinafter called the “first predetermined speed”) NEref1. The first predetermined speed NEref1 will be explained later.

Since the engine speed NE is less than the first predetermined speed NEref1 generally in a program loop immediately after the engine start, the result in S26 is negative and the program proceeds to S28, in which it is determined whether the bit of an acceleration determining flag (explained later; indicated by “acceleration flag” in the drawing) is 0. Since the initial value of this flag is also 0, the result in S28 in the first program loop is generally affirmative and the program proceeds to S30.

In S30, it is determined whether the acceleration (precisely, the rapid acceleration) is instructed to the engine 30 by the operator, i.e., whether the engine 30 is in the operating condition to accelerate the boat 1 (rapidly). This determination is made by checking as to whether the throttle valve 38 is operated in the opening direction rapidly.

Specifically, the change amount DTH of the throttle opening TH detected in S14 is compared with a second predetermined value (predetermined value) DTHref2 and when the change amount DTH is equal to or greater than the second predetermined value DTHref2, it is determined that the throttle valve 38 is operated in the opening direction rapidly, i.e., the acceleration is instructed to the engine 30. The second predetermined value DTHref2 is set as a criterion (e.g., 0.5 degree) for determining whether the acceleration is instructed to the engine 30.

When the result in S30 is negative, i.e., it is determined that neither the acceleration nor the deceleration is instructed to the engine 30, in other words, it is immediately after the engine start or in the condition where the boat 1 cruises at constant speed, the program proceeds to S32, in which the first and second solenoid valves 86 a, 86 b (indicated by “1ST SOL,” “2ND SOL” in the drawing) are both made ON to select the second speed in the transmission 46, and to S34, in which the bit of the acceleration determining flag is reset to 0.

On the other hand, when the result in S30 is affirmative, the program proceeds to S36, in which it is determined whether the engine speed NE is greater than a predetermined speed NErefa. The predetermined speed NErefa is set as a criterion (e.g., 3000 rmp) for determining that, when the engine speed NE is above this value, the boat speed has already reached the medium level (intermediate speed) and the engine speed NE is relatively high (e.g., even if the gear position is changed from the second speed to the first speed, the torque amplification through the transmission 46 can not be expected).

When the result in S36 is affirmative, the program proceeds to S38, in which the bit of an at-acceleration fuel amount increasing flag (initial value 0; hereinafter called the “fuel increasing flag”) indicating that a fuel amount to be supplied to the engine 30 is increased is set to 1. When the bit of this flag is set to 1, in another program which is not shown, control for increasing the fuel amount to be supplied to the engine 30 is conducted, in other words, a basic fuel injection amount calculated based on the output of the crank angle sensor 102 (i.e., the engine speed NE), etc., is increased by a predetermined amount to increase the output torque of the engine 30, thereby improving the acceleration performance. When the bit of the fuel increasing flag is reset to 0, the control for increasing the fuel amount is not conducted and normal fuel injection control is conducted.

After the step of S38, the aforementioned process of S32 and S34 is conducted and the program is terminated. Thus, when it is determined that the acceleration is instructed and the engine speed NE is greater than the predetermined speed NErefa, only the fuel amount to be supplied is increased without changing the gear position, i.e., with the second speed being maintained.

When the result in S36 is negative, i.e., the engine speed NE is equal to or less than the predetermined speed NErefa, the program proceeds to S40, in which a slip ratio S indicating the rotating condition of the propeller 42 is detected or calculated. The slip ratio S is calculated based on theoretical velocity Va and actual velocity V of the boat 1, using Equation (1) as follows: Slip ratio S=(Theoretical velocity Va(Km/h)−Actual velocity V(Km/h))/Theoretical velocity Va(Km/h)  Equation (1)

In Equation (1), the actual velocity V is obtained based on the output of the boat speed sensor 130. The theoretical velocity Va is calculated based on the operating condition of the engine 30 and transmission 46 and specification of the propeller 42, as can be seen in Equation (2) as follows: Theoretical velocity Va(Km/h)=(Engine speed NE(rpm)×Propeller pitch (inch)×60×2.54×10⁻⁵)/(Gear ratio of gear position)  Equation (2)

In Equation (2), the propeller pitch is a value indicating a theoretical distance by which the boat 1 proceeds per one rotation of the propeller 42. The gear ratio of gear position is a gear ratio of the currently-selected gear position in the transmission 46, e.g., is 2.0 in the second speed, as mentioned above. The value of 60 is used for converting the engine speed NE for one minute into that for one hour, and the value of 2.54×10⁻⁵ is used for converting a unit of the propeller pitch from inch to kilometer.

The program proceeds to S42, in which it is determined whether the propeller 42 is in a predetermined rotating condition. This determination is made by comparing the slip ratio S of the propeller 42 detected in S40 with a predetermined slip ratio Sref.

Specifically, when the slip ratio S is equal to or less than the predetermined slip ratio Sref, i.e., when the slip ratio S is relatively small and the grip force of the propeller 42 is relatively large, the propeller 42 is determined to be in the predetermined rotating condition. In contrast, when the slip ratio S is greater than the predetermined slip ratio Sref, i.e., when the slip ratio S is relatively large due to idle rotation of the propeller 42 or the like and the grip force is relatively small, the propeller 42 is determined to be not in the predetermined rotating condition.

The predetermined rotating condition is a condition where the grip force of the propeller 42 is relatively large, and the predetermined slip ratio Sref is set as a criterion (e.g., 0.3) for determining whether the propeller 42 is in such the rotating condition.

When the result in S42 is negative, the remaining steps are skipped, while when the result is affirmative, the program proceeds to S44, in which the first and second solenoid valves 86 a, 86 b are both made OFF to change the transmission 46 (shift down the gear) from the second speed to the first speed.

Then the program proceeds to S46, in which the bit of the fuel increasing flag is set to 1 to increase the fuel amount to be supplied to the engine 30. Thus, when it is determined that the acceleration is instructed and the engine speed NE is equal to or less than the predetermined speed NErefa, the fuel amount supplied to the engine 30 is increased and the gear position is changed from the second speed to the first speed. As a result, the output torque of the engine 30 is increased due to the increase in the fuel supply, while the output torque is amplified through the transmission 46 (more precisely, the transmission mechanism 50) which has been shifted down to the first speed and transmitted to the propeller 42 via the drive shaft 52 a and propeller shaft 44, thereby improving the acceleration performance.

The program proceeds to S48, in which the bit of the acceleration determining flag is set to 1 and the present program is terminated. Specifically, the bit of the acceleration determining flag is set to 1 when the acceleration is determined to be instructed to the engine 30 and the transmission 46 is changed from the second speed to the first speed, and otherwise, reset to 0. Upon setting of the bit of the acceleration determining flag to 1, the result in S28 in the next and subsequent loops becomes negative and the program skips S30, S36, S40 and S42 and proceeds to S44 to S48.

When the engine speed NE is gradually increased due to the increase in the fuel supply to the engine 30 and the acceleration is completed (i.e., the acceleration range is saturated), the engine speed NE reaches the first predetermined speed NEref1. Subsequently, in the next program loop, the result in S26 becomes affirmative and the program proceeds to S50 onward. The first predetermined speed NEref1 is set to a relatively high value (e.g., 6000 rpm) as a criterion for determining whether the acceleration is completed.

In S50, it is determined whether the engine speed NE is stable, i.e., the engine 30 is stably operated. This determination is made by comparing an absolute value of the change amount DNE of the engine speed NE calculated in S22 with a first prescribed value DNEref1. When the absolute value is less than the first prescribed value DNEref1, the engine speed NE is determined to be stable. The first prescribed value DNEref1 is set as a criterion (e.g., 500 rpm) for determining whether the engine speed NE is stable, i.e., the change amount DNE is relatively small.

When the result in S50 is negative, the program is terminated, while, when the result is affirmative, the program proceeds to S52, in which the first and second solenoid valves 86 a, 86 b are both made ON, whereby, in the case where the first speed is selected, the transmission 46 is changed (the gear is shifted up) from the first speed to the second speed. It causes the increase in the rotational speed of the drive shaft 52 a and that of the propeller shaft 44, so that the boat speed reaches the maximum speed (in a range of the engine performance), thereby improving the speed performance.

After the step of S52, the program proceeds to S54 and S56, in which the bit of the second speed flag is set to 1 and the bit of the third speed flag is reset to 0. Then in S58, the bit of the fuel increasing flag is reset to 0, whereafter the program of fuel increasing control is terminated or stopped.

Upon setting of the bit of the second speed flag to 1 in S54, the result in S24 in the next and subsequent loops becomes negative and the program proceeds to S60. Thus, when the bit of the second speed flag is set to 1, i.e., when the gear position is changed to the second speed after the acceleration in the first speed is completed, the process of S60 onward is conducted.

In S60, it is determined whether the switch 126 outputs the ON signal, i.e., whether the fuel consumption decreasing command for the engine 30 is inputted by the operator. When the result in S60 is affirmative, the program proceeds to S62, in which it is determined whether the engine speed NE is equal to or greater than a second gear change predetermined speed (hereinafter called the “second predetermined speed”) NEref2. The second predetermined speed NEref2 is set to a value (e.g., 5000 rpm) slightly lower than the first predetermined speed NEref1, as a criterion for determining whether it is possible to change the gear position to the third speed (explained later).

When the result in S62 is affirmative, the program proceeds to S64, in which, similarly to S50, it is determined whether the engine speed NE is stable. Specifically, the absolute value of the change amount DNE of the engine speed NE is compared with a second prescribed value DNEref2. When the absolute value is less than the second prescribed value DNEref2, the engine speed NE is determined to be stable, and vice versa. The second prescribed value DNEref2 is set as a criterion (e.g., 500 rpm) for determining whether the change amount DNE is relatively small and the engine speed NE is stable.

When the result in S64 is negative or that in S60 or S62 is negative, the process of S52 to S58 is conducted, whereafter the program is terminated with the second speed being maintained. When the result in S64 is affirmative, the program proceeds to S66, in which the first solenoid valve 86 a is made ON and the second solenoid valve 86 b is made OFF to change the transmission 46 (shift up the gear) from the second speed to the third speed. As a result, the engine speed NE is decreased, thereby decreasing the fuel consumption, i.e., improving the fuel efficiency.

Next, the program proceeds to S68, in which the bit of the second speed flag is reset to 0, and to S70, in which the bit of the third speed flag is set to 1. Thus, the third speed flag is set to 1 when the gear position is changed from the second speed to the third speed after the acceleration is completed, and otherwise, reset to 0.

In a program loop after the bit of the third speed flag is set to 1, the result in S18 is negative and the process of S66 to S70 is conducted, whereafter the program is terminated with the third speed being maintained.

When the result in S16 is affirmative, i.e., the deceleration is determined to be instructed to the engine 30, the program proceeds to S72, in which the first and second solenoid valves 86 a, 86 b are both made ON to change the transmission 46 to the second speed. Then the program proceeds to S74, S76, S78 and S80, in which all bits of the second speed flag, third speed flag, acceleration determining flag and fuel increasing flag are reset to 0, whereafter the program is terminated.

Under the condition where the second speed is established, when the lever 122 is manipulated by the operator to change the shift position of the transmission 46 to neutral, the result in S10 is affirmative and the program proceeds to S82, in which the first and second solenoid valves 86 a, 86 b are both made OFF to change the transmission 46 from the second speed to the first speed.

FIG. 6 is a time chart for explaining the operation of the FIG. 5 flowchart.

As shown in FIG. 6, when the transmission 46 is set in the second speed and the throttle valve 38 is opened upon the manipulation of the lever 122 by the operator, at the time t1, the acceleration is determined to be instructed to the engine 30 (S30).

As indicated by solid lines in the drawing, when the engine speed NE is greater than the predetermined speed NErefa at the time t1, the bit of the fuel increasing flag is set to 1 to increase the output torque of the engine 30 (S38). The gear position remains in the second speed.

The explanation is made on the case that the engine speed NE is equal to or less than the predetermined speed NErefa, which is indicated by imaginary lines. Immediately after the acceleration is started, the propeller 42 tends to be rotated idly because it draws in air bubbles generated around the hull 12, and therefore the grip force thereof becomes relatively small so that the slip ratio S rises. After that, as the air bubbles decrease with time, the decreased grip force is gradually increased, i.e., the slip ratio S is gradually decreased. At the time t2, when it is determined that the slip ratio S is equal to or less than the predetermined slip ratio Sref (S40, S42), the bit of the fuel increasing flag is set to 1 to increase the fuel amount supplied to the engine 30 and the gear position is changed from the second speed to the first speed (S44, S46).

The engine speed NE is gradually increased due to the increase in the fuel supply or the like. When, at the time t3, it is determined that the engine speed NE is equal to or greater than the first predetermined speed NEref1 (S26) and also that the change amount DNE is less than the first prescribed value DNEref1 (S50), in the case where the first speed is selected, the gear position is changed from the first speed to the second speed and the bit of the fuel increasing flag is reset to 0 to terminate the fuel increasing control (S52, S58).

When, at the time t4, the switch 126 is manipulated by the operator to input the fuel consumption decreasing command (S60) and also when, at the time t5, it is determined that the engine speed NE is equal to or greater than the second predetermined speed NEref2 (S62) and the change amount DNE is less than the second prescribed value DNEref2 (S64), the gear position is changed from the second speed to the third speed (S66).

Then, when the throttle valve 38 is closed upon, for example, the manipulation of the lever 122 by the operator to input a regulation command for decreasing the engine speed NE and, at the time t6, the deceleration is determined to be instructed (S16), the gear position is changed from the third speed to the second speed (S72).

As stated above, the embodiment is configured to have an apparatus and a method for controlling operation of an outboard motor (10) adapted to be mounted on a stern of a boat (12) and having an internal combustion engine (30) to power a propeller (42) through a propeller shaft (44), and a transmission (46) installed at a location between the engine and the propeller shaft, the transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, comprising: an engine speed detector (crank angle sensor 102, ECU 110, S20) that detects speed of the engine (NE); an acceleration instruction determiner (ECU 110, S30) that determines whether acceleration is instructed to the engine when the second speed is established; and a controller (ECU 110, S36, S38) that controls operation of the engine to increase a fuel amount to be supplied to the engine (30) when the detected engine speed (NE) is greater than a predetermined speed (NErefa).

Thus, it is configured such that, under the condition where the second speed is selected, when the acceleration is instructed to the engine 30 and the engine speed NE is greater than the predetermined speed NErefa, the fuel amount to be supplied to the engine 30 is increased.

In other words, in the case that the acceleration is instructed when the engine speed NE is relatively high, even if the gear position is changed from the second speed to the first speed, since the torque amplification through the transmission 46 can not be expected, only the fuel amount is increased without changing the gear position, i.e., with the second speed being maintained.

With this, the output torque of the engine 30 can be increased by increasing the fuel amount. Further, since the gear position is not changed to the first speed unnecessarily, it becomes possible to prevent the boat speed from decreasing, thereby reliably improving the acceleration performance of immediately after the acceleration is started.

Furthermore, in the apparatus and method, the controller controls operation of the transmission to change the gear position from the second speed to the first speed, in addition to increase the fuel amount to be supplied to the engine, when the detected engine speed is not greater than the predetermined speed (NErefa; S36, S44, S46).

Thus, when the engine speed NE is not greater than (equal to or less than) the predetermined speed NErefa, i.e., the engine speed NE is relatively low, the fuel amount to be supplied to the engine 30 is increased and the gear position is changed from the second speed to the first speed.

With this, the output torque of the engine 30 can be increased by increasing the fuel amount to be supplied, and since this output torque is amplified through the transmission 46 which has been shifted down to the first speed and transmitted to the propeller 42, the boat speed immediately starts increasing, thereby improving the acceleration performance of immediately after the acceleration is started.

As a result, the operation of the transmission 46 and engine 30 during acceleration can be controlled appropriately in accordance with the cruising condition of the boat 1, i.e., the operating condition of the engine 30, thereby reliably improving the acceleration performance of immediately after the acceleration is started.

In the apparatus and method, the controller includes: a slip ratio detector (110, 130, S40) that detects a slip ratio (S) of the propeller (42) based on theoretical boat velocity (Va) and actual boat velocity (V); and controls operation of the transmission to change the gear position from the second speed to the first speed, in addition to increase the fuel amount to be supplied to the engine, if detected slip ratio (S) is equal to or less than a predetermined slip ratio (Sref2) when the detected engine speed (NE) is not greater than the predetermined speed (NErefa; S36, S42, S44, S46)

With this, in addition to the above effects, it becomes possible to change the gear position from the second speed to the first speed at the appropriate time when the grip force of the propeller 42 is increased after the acceleration. As a result, the output torque of the engine 30 is increased and amplified through the transmission 46 and transmitted to the propeller 42, so that the boat speed immediately starts increasing, thereby improving the acceleration performance of immediately after the acceleration is started.

In the apparatus and method, the acceleration instruction determiner includes: a throttle opening change amount detector (96, 110, S14) that detects a change amount of throttle opening (DTH) of the engine; and determines that the acceleration is instructed when the detected change amount of the throttle opening (DTH) is equal to or greater than a predetermined value (DTHref2; S30).

With this, it becomes possible to accurately determine whether the acceleration is instructed.

The apparatus and method further include: a neutral position determiner (100, 110, S10) that determines whether the transmission is in a neutral position; and the controller controls the operation of the transmission to change the gear position from the second speed to the first speed when the second speed is established and the transmission is determined to be in the neutral position (S82).

The apparatus and method further include: a hydraulic clutch (C2) that is installed in the transmission and adapted to establish the speeds including the first speed and the second speed; and the controller controls the operation of the transmission to establish the first speed when the clutch is not supplied with hydraulic pressure.

Specifically, the transmission 46 is configured to establish the second speed in the normal operation, and establish the first speed when the transmission clutch (C2) is not supplied with the hydraulic pressure from the pump 60, while establishing the second speed when it is supplied.

With this, it becomes possible to limit the operation of the pump 60, thereby decreasing the fuel consumption of the engine 30. In other words, when the transmission 46 is in the neutral position, the gear position is changed from the second speed to the first speed (in which the hydraulic pressure is not supplied to the transmission clutch (C2) from the pump 60), thereby achieving the above effects.

It should be noted that the actual velocity V of the boat 1 can be detected by, in place of the boat speed sensor 130, a GPS (Global Positioning System) for instance.

It should also be noted that, although the predetermined speed NErefa, first and second predetermined values DTHref1, DTHref2, displacement of the engine 30 and other values are indicated with specific values in the foregoing, they are only examples and not limited thereto.

Japanese Patent Application No. 2009-285808, filed on Dec. 16, 2009 is incorporated by reference herein in its entirety.

While the invention has thus been shown and described with reference to specific embodiments, it should be noted that the invention is in no way limited to the details of the described arrangements; changes and modifications may be made without departing from the scope of the appended claims. 

What is claimed is:
 1. An apparatus for controlling operation of an outboard motor adapted to be mounted on a stern of a boat and having an internal combustion engine to power a propeller through a propeller shaft, and a transmission installed at a location between the engine and the propeller shaft, the transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, comprising: an engine speed detector that detects speed of the engine; a throttle opening change amount detector that detects a change amount of throttle opening of the engine; and a controller that controls operation of the transmission and the engine after the second speed is established, wherein the first speed and the second speed are each forward speeds with the first speed having a higher gear ratio than the second speed, and wherein the controller: controls operation of the transmission to maintain the second speed and operation of the engine to supply a basic fuel amount calculated based on the detected engine speed in response to the detected change amount of the throttle opening being less than a predetermined value, controls operation of the transmission to maintain the second speed and operation of the engine to increase a fuel amount to be supplied to the engine by a predetermined amount more than the basic fuel amount in response to the detected change amount of the throttle opening being equal to or greater than the predetermined value and in response to the detected engine speed being greater than a predetermined speed, the predetermined speed being a fixed value set regardless of the throttle opening, and controls operation of the transmission to change the gear position from the second speed to the first speed and of the engine to increase the fuel amount to be supplied to the engine by the predetermined amount more than the basic fuel amount in response to the detected change amount of the throttle opening being equal to or greater than the predetermined value and in response to the detected engine speed being equal to or less than the predetermined speed.
 2. The apparatus according to claim 1, wherein the controller includes: a slip ratio detector that detects a slip ratio of the propeller based on theoretical boat velocity and actual boat velocity; and controls operation of the transmission to change the gear position from the second speed to the first speed, in addition to increase the fuel amount to be supplied to the engine in response to the detected slip ratio being equal to or less than a predetermine slip ratio and in response to the detected engine speed being equal to or less than the predetermined speed.
 3. The apparatus according to claim 1, further including: a neutral position determiner that determines whether a shift position of the transmission is changed to a neutral position; and the controller controls the operation of the transmission to change the gear position from the second speed to the first speed in response to the determination that the shift position is changed to the neutral position when the second speed is established.
 4. The apparatus according to claim 3, further including: a hydraulic clutch that is installed in the transmission and adapted to establish the speeds including the first speed and the second speed; and the controller controls the operation of the transmission to establish the first speed when the clutch is not supplied with hydraulic pressure.
 5. A method for controlling operation of an outboard motor adapted to be mounted on a stern of a boat and having an internal combustion engine to power a propeller through a propeller shaft, and a transmission installed at a location between the engine and the propeller shaft, the transmission being selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, comprising the steps of: detecting speed of the engine; detecting a change amount of throttle opening of the engine; and controlling operation of the transmission and the engine after the second speed is established, wherein the first speed and the second speed are each forward speeds with the first speed having a higher gear ratio than the second speed, and wherein the step of the controlling includes: controlling operation of the transmission to maintain the second speed and operation of the engine to supply a basic fuel amount calculated based on the detected engine speed in response to the detected change amount of the throttle opening being less than a predetermined value, controlling operation of the transmission to maintain the second speed and of the engine to increase a fuel amount to be supplied to the engine by a predetermined amount more than the basic fuel amount in response to the detected change amount of the throttle opening being equal to or greater than the predetermined value and in response to the detected engine speed being greater than a predetermined speed, the predetermined speed being a fixed value set regardless of the throttle opening, and controlling operation of the transmission to change the gear position from the second speed to the first speed and of the engine to increase the fuel amount to be supplied to the engine by the predetermined amount more than the basic fuel amount in response to the detected change amount of the throttle opening being equal to or greater than the predetermined value and in response to the detected engine speed being equal to or less than the predetermined speed.
 6. The method according to claim 5, wherein the step of controlling includes the step of: detecting a slip ratio of the propeller based on theoretical boat velocity and actual boat velocity; and controls operation of the transmission to change the gear position from the second speed to the first speed, in addition to increase the fuel amount to be supplied to the engine in response to the detected slip ratio being equal to or less than a predetermined slip ratio and in response to the detected engine speed being equal to or less than the predetermined speed.
 7. The method according to claim 5, further including the step of: determining whether a shift position of the transmission is changed to a neutral position; and the step of controlling controls the operation of the transmission to change the gear position from the second speed to the first speed in response to the determination that the shift position is changed to the neutral position when the second speed is established.
 8. The method according to claim 7, wherein the step of controlling controls the operation of the transmission to establish the first speed when a hydraulic clutch adapted to establish the speeds including the first speed and the second speed is not supplied with hydraulic pressure. 